Copper sulfides containing arsenic or antimony are commonly-occurring minerals. Arsenic-containing copper sulfides include sulpharsenites, such as enargite (Cu3AsS4), and sulpharsenates, such as tennantite (Cu12As4S13). Antimony-containing copper sulfides include sulfantimonites, such as famatinite (Cu3SbS4), and sulphantimonates, such as tetrahedrite (Cu12Sb4S13). It is difficult to recover the copper from such minerals. For example enargite has proven resistant to virtually every leaching process other than total pressure oxidation in autoclaves with oxygen at temperatures exceeding 200° C., which is not an economic process. Additionally, submitting enargite-containing copper concentrates to smelters for toll treatment incurs heavy financial penalties due to the high arsenic levels, when they are accepted at all.
There are two different approaches to leaching copper from concentrate, namely, bioleaching and chemical leaching. The distinction between bioleaching and chemical leaching is well established in the copper leaching art.
Bioleaching relies on the presence of bacteria or other microorganisms to enable the recovery of copper. Typically, bioleaching requires a slurry containing carbon dioxide and other microbial nutrients, sulfide concentrate and microorganisms as well as innoculant tanks, microbial monitoring systems, and control of acidity, pH and redox potential. Bioleaching of copper concentrates is typically very slow, with incomplete recoveries achieved even after many weeks to months of leaching.
Chemical leaching relies solely on a chemical interaction between minerals and does not require microorganisms. Chen, U.S. Pat. No. 3,930,969, discloses a process whereby enargite is anodically dissolved in an electrolytic cell containing a chloride solution with activated carbon added to the concentrate slurry. Approximately 28% of the copper was recovered.
It would be desirable to be able to recover copper from mineral concentrates containing copper arsenic sulfosalt and copper antimony sulfosalt minerals by an economically viable, hydrometallurgical chemical leaching process.